U.S. forces searched several times last year the Iraqi military base from which 380 tons of explosives vanished — including one check a week before Saddam Hussein was driven out of power. But the military saw no signs of a huge quantity of munitions, Pentagon officials told FOX News.

A timeline provided by the Defense Department is significant because officials from the new Iraqi interim government told the International Atomic Energy Agency (search) two weeks ago that the explosives were stolen sometime after coalition forces took control of Baghdad.

The IAEA reported the disappearance to the U.N. Security Council (search) on Monday, the same day the New York Times ran a front-page story on the topic. The story started a firestorm of debate that has consumed the presidential race in its closing days, forced the Pentagon to account for its actions and raised questions of media bias.

The explosives were being kept at the Al-Qaqaa (search) installation south of Baghdad. The munitions included HMX and RDX, key components in plastic explosives, which insurgents in Iraq have used in bomb attacks. The IAEA was monitoring the munitions because HMX is a "dual use" substance powerful enough to ignite the fissile material in an atomic bomb and set off a nuclear chain reaction.

On April 3, 2003, elements of the Army's 3rd Infantry Division (search) made it to Al-Qaqaa, where they were engaged by Iraqi forces from inside the facility, Defense officials told FOX News.

The 3rd Infantry soldiers stayed long enough to battle the Iraqis and to give the facility a brief inspection before heading out to continue on their prime objective — reaching the Iraqi capital.

A day or so after Baghdad fell on April 9, 2003, troops from the 101st Airborne Division's (search) 2nd Brigade arrived at Al-Qaqaa.

One officer with the 101st said looters had already gone through the facility.

The soldiers "secured the area they were in and looked in a limited amount of bunkers to ensure chemical weapons were not present in their area," Lt. Col. Fred Wellman, deputy public affairs officer for the unit, wrote in an e-mail to The Associated Press. "Bombs were found but not chemical weapons in that immediate area.

"Orders were not given from higher to search or to secure the facility or to search for HE type munitions, as they [high-explosive weapons] were everywhere in Iraq," he wrote.

On May 8, 2003, a team from the 75th Exploitation Task Force (search) arrived at Al-Qaqaa to search it. The task force followed up with additional searches on May 11 and May 27.

The 75th Exploitation Task Force, which was in charge of directing the search operation for weapons of mass destruction in Iraq, did not find any evidence of the explosives.

The Pentagon investigation is continuing, and there is some thought that trucks operated by Saddam's regime may have been in the vicinity of the facility in late March.

The explosives at Al-Qaqaa had been housed in storage bunkers at the facility. U.N. nuclear inspectors placed fresh seals over the bunker doors in January 2003. The inspectors visited Al-Qaqaa for the last time on March 15, 2003, and reported that the seals were not broken; therefore, the weapons were still there at the time. The team then pulled out of the country in advance of the invasion.

Reporters Offer First-Hand Accounts

Reporters who were embedded with the U.S. military at the time also have offered first-hand accounts of what they saw at Al-Qaqaa.

FOX News' Dana Lewis was with the 2nd Brigade of the 101st Airborne Division when it stopped at the site on April 10 for 24 hours before continuing on to Baghdad.

"It was sealed in the sense that when we arrived, no one was inside," Lewis said, adding that there were dozens of abandoned Iraqi tanks outside the facility.

"Inside, we walked around dozens of concrete bunkers, which were still sealed. Many still had padlocks on the doors and in another part of this giant walled compound, we saw dozens and dozens of rockets, most of them damaged from air strikes."

Lewis noted that he did not see any IAEA tags during his brief time at Al-Qaqaa.

Associated Press correspondent Chris Tomlinson, who was embedded with the 3rd Infantry but didn't go to Al-Qaqaa, described the search of Iraqi military facilities south of Baghdad as brief, cursory missions to seek out hostile troops, not to inventory or secure weapons.

The enormous size of the bases, the rapid pace of the advance on Baghdad and a limited number of troops made it impossible for U.S. commanders to allocate any soldiers to guard any of the facilities after making a check, Tomlinson said.

NBC correspondent Lai Ling Jew, who was with the 101st, told MSNBC that "there wasn't a search" of Al-Qaqaa.

"The mission that the brigade had was to get to Baghdad," she said. "As far as we could tell, there was no move to secure the weapons, nothing to keep looters away."

Wellman, the 101st Airborne spokesman, said he does not know if any troops were left at the facility once combat troops from the 2nd Brigade left.

The IAEA had pulled out of Iraq in 1998, and by the time it returned in 2002, it confirmed that 35 tons of HMX that had been placed under IAEA seal were missing.

IAEA chief Mohamed ElBaradei (search) told the United Nations in February 2003 that Iraq had declared that "HMX previously under IAEA seal had been transferred for use in the production of industrial explosives, primarily to cement plants as a booster for explosives used in quarrying."

"However, given the nature of the use of high explosives, it may well be that the IAEA will be unable to reach a final conclusion on the end use of this material," ElBaradei warned at the time.

He did not specifically mention Al-Qaqaa in his February 2003 briefing to the United Nations, and the agency has not said whether it separately informed the United States.

FOX News' Bret Baier, Dana Lewis and The Associated Press contributed to this report.